textproduct: Rapid City

KEY MESSAGES

- Unsettled and cooler through the weekend, with daily chances for thunderstorms.

- Strong to severe thunderstorms expected this afternoon and evening.

- Wildfire smoke will linger through Thursday. There could be some improvement toward the end of the week.

DISCUSSION

(This Evening Through Wednesday) Issued at 1200 PM MDT Wed Aug 12 2026

Water vapor imagery shows broad upper ridging across the south central CONUS. Upper flow over the CWA is nearly zonal, but active WSW flow over the western CONUS is quickly approaching, along with monsoonal moisture. A strong shortwave is over NW UT/eastern ID/western WY pushing eastward toward the CWA. Forcing ahead of the wave is bringing showers and thunderstorms to much of WY, including NE WY into the Black Hills and far SW SD. Deep SE low level flow is keeping moisture-rich air across the CWA even into NE WY, with dewpoints in the upper 50s to upper 60s areawide. MLCAPE of 1000- 1500 J/kg is expected as the cap quickly erodes this afternoon. 0- 6km shear will increase this afternoon to 40-60kt, supporting strong to severe storms, including isolated supercells. Large hail and damaging winds will be the main threats. Heavy rainfall will also be supported by PWATs of 150-175% of normal. CAMs show the current precip continuing northeastward, then storms developing afterward by mid afternoon across NE WY and the Black Hills area...then pushing eastward across the western SD plains. Generally quiet weather is expected overnight tonight but could still see some linger showers through early Thursday morning. Upper flow becomes more southwesterly on Thursday as another strong wave crosses the region. This will likely bring another round of high-coverage showers and thunderstorms. Instability will be slightly weaker tomorrow and shear will be much weaker, so organized severe weather is not expected. However, with PWATS nearing 200% of normal, hoping to see more much-needed precipitation though models are differing on QPF amounts and placement. Moist monsoonal flow will keep daily chances for storms across the region through the end of this and the weekend, along with near to slightly below average temps. Can't rule out strong/severe storms over the weekend.

AVIATION

(For the 18Z TAFS Through 18Z Thursday) Issued At 1135 AM MDT Wed Aug 12 2026

Showers and storms are moving into the area. Thunderstorms will develop and grow this afternoon and continue into this evening. Local IFR conditions, strong gusty erratic winds, and hail may be encountered near any storms.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.